It is known that light having a relatively high amount of blue light may correlate with melatonin suppression in humans and other mammals, and that melatonin is a key hormone involved in the entrainment (synchronization) of the circadian rhythms of physiological functions including sleep timing and many others. Therefore, a low-blue, low correlated color temperature (CCT) (e.g., 2000 K) spectrum at low lux levels encourages melatonin production and helps a user of a light source embodying such spectrum to promote sleep. A high-blue, high CCT (e.g. 7000 K) spectrum at high lux levels generally suppresses melatonin production, and may assist a user of a light source that embodies such spectrum to awaken in the morning and feel alert during the day. This relatively new application of lighting is known as Circadian Lighting, or as a subset of Human-centric Lighting.
Some light-emitting diode (LED)-based lamps which may pertain to the effect of light on human melatonin production or suppression, are known. United States Patent Application Publication No. 2015/0062892 describes a light source formed to include a first LED emission (e.g., one or more LEDs emitting a first spectrum) and a second LED emission (e.g., one or more LEDs emitting a second spectrum), where the first and second LED emissions are combined in a first ratio and in a second ratio such that while changing from the first ratio to the second ratio the relative circadian stimulation is varied while maintaining a color rendering index above 80.
United States Patent Application Publication No. 2012/0008326 describes a lighting device that includes a light-emitting device being able to emit a visible light and a light-filtering device being close to the light-emitting device. When the light-emitting device emits the visible light, the light-filtering device is able to filter a blue light component of the visible light so as to reduce the blue light component within the visible light emitted by the light-emitting device, thereby reducing the effects on suppressing the melatonin caused by the visible light.
United States Patent Application Publication No. 2014/0228914 describes solid-state light-emitting devices that include multiple LED components providing adjustable melatonin suppression effects. Multiple LED components may be operated simultaneously according to different operating modes according to which their combined output provides the same or similar chromaticity, but provide melatonin suppressing effects that differ by at least a predetermined threshold amount between the different operating modes.